Scientists probing Mars rover's odd behavior

The mystery began over the weekend when Spirit failed to notify controllers on Earth of its orientation after driving. It deepened when the solar-powered rover did not record its activities to its memory.

Scientists at NASA's Jet Propulsion Laboratory in Pasadena are running diagnostic tests this week to figure out the problem.

One possible explanation is that cosmic rays may have hit Spirit's electronics.

Spirit and its twin Opportunity have been roaming the Martian equatorial plains since 2004.